Back-Side Illumination Image Sensor Light Guidance via Refractive Index
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In image sensing devices of back-side illumination, the thin photoelectric conversion portion fails to absorb incident light effectively, leading to light penetration and potential color mixing between pixels, as existing solutions like cylindrical metal layers are not entirely effective in preventing light from reaching adjacent pixels.
Innovation Solution
The implementation of a high refractive index region and a reflection layer in the image sensing device, where the high refractive index region is positioned to overlap with the photoelectric conversion portion and the reflection layer is placed on the opposite side to efficiently reflect light back to the conversion portion, reducing color mixing by guiding and reflecting light within the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the photoelectric conversion portion is made thinner to enable back-side illumination, then light can be received from the back surface, but light absorption becomes insufficient and color mixing between pixels occurs
Solution Approach 1:
A light guide layer is introduced as an intermediary component between the incident light and the photoelectric conversion portion. This light guide layer has a higher refractive index than the surrounding resin layer, enabling it to effectively guide and concentrate light onto the thin photoelectric conversion portion, thereby improving light absorption efficiency while maintaining back-side illumination capability
Solution Approach 2:
The refractive index parameter is strategically changed by using a light guide layer with a higher refractive index than the resin layer. This parameter change enables effective light guidance and concentration, allowing the thin photoelectric conversion portion to absorb sufficient light for back-side illumination operation
2Reliability
If a cylindrical metal layer is added to reflect light, then color mixing is reduced, but device complexity increases
Solution Approach 1:
The light guide layer serves as a non-metallic intermediary that performs light guidance and concentration functions. This approach achieves color mixing prevention through optical parameter control (refractive index difference) rather than metallic reflection, thereby reducing device complexity while maintaining effectiveness
Solution Approach 2:
The metallic reflection system is replaced with an optical guidance system based on refractive index differences. This substitution eliminates the need for cylindrical metal layers and their associated complex structures, achieving the same color mixing prevention through non-metallic light guidance mechanisms
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances light absorption and reduces color mixing between pixels, improving the sensitivity and accuracy of the image sensing device by effectively managing light penetration and reflection.
Implementation Method 1
A refractive index of the first non-metal region is higher than a refractive index of the second non-metal region
Implementation Method 2
a reflection layer arranged on an opposite side of the first non-metal region to the semiconductor substrate
Data Source
AI summary
An image sensing device includes a plurality of photoelectric conversion portions. The device further includes a semiconductor substrate having a first surface for receiving incident light and a second surface on an opposite side to the first surface, the photoelectric conversion portions being provided therein, a first non-metal region arranged on a second surface side and arranged at a position at least partially overlapping with the photoelectric conversion portions, a second non-metal region arranged to be in contact with a side surface of the first non-metal region, and a reflection layer arranged on an opposite side of the first non-metal region to the semiconductor substrate. A refractive index of the first non-metal region is higher than a refractive index of the second non-metal region.